How long does the back up battery last on a garage door opener? Wilson February 24, 2021 18:51 Updated Only an estimated time of 1-2 days on normal usage in an electrical power outage. Related articles Why is my wall button working but my remote is not on my garage door opener? Where can I locate information about warranty on my specific product? Why is my key pad not working on my garage door opener? Comments 0 comments Please sign in to leave a comment.